Laminar flow restrictor and seal for same

ABSTRACT

Apparatuses for controlling gas flow are important components for delivering process gases for semiconductor fabrication. These apparatuses for controlling gas flow frequently rely on flow restrictors which can provide a known flow impedance of the process gas. In one embodiment, a flow restrictor is disclosed, the flow restrictor constructed of a plurality of layers, one or more of the layers having a flow passage therein that extends from a first aperture at a first end of the flow restrictor to a second aperture at a second end of the flow restrictor.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 17/710,290, filed Mar. 31, 2022, which is (1) a continuation inpart of U.S. patent application Ser. No. 16/985,540, filed Aug. 5, 2020,now U.S. Pat. No. 11,639,865, which in turn claims the benefit of U.S.Provisional Patent Application No. 62/882,794, filed Aug. 5, 2019; and(2) a continuation in part of U.S. patent application Ser. No.16/985,635, filed Aug. 5, 2020, now U.S. Pat. No. 11,585,444, which inturn claims the benefit of U.S. Provisional Patent Application No.62/882,814, filed Aug. 5, 2019, the entireties of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

Mass flow control has been one of the key technologies in semiconductorchip fabrication. Apparatuses for controlling mass flow are importantfor delivering known flow rates of process gases for semiconductorfabrication and other industrial processes. Such devices are used tomeasure and accurately control the flow of fluids for a variety ofapplications. This control may be achieved through the use of preciselycalibrated laminar flow restrictors which are effectively sealed toprevent bypass flow pas the laminar flow restrictors.

As the technology of chip fabrication has improved, so has the demand onthe apparatuses for controlling flow. Semiconductor fabricationprocesses increasingly require increased performance, including moreaccurate measurements, lower equipment costs, improved transientresponse times, and more consistency in timing in the delivery of gases.In order to improve the consistency in gas delivery, improved flowrestrictors and associated seals are desired.

SUMMARY OF THE INVENTION

The present technology is directed to a laminar flow restrictor for usein a mass flow controller or other gas delivery device and seals to sealthe aforementioned laminar flow restrictors. One or more of these gasdelivery devices may be used in a wide range of processes such assemiconductor chip fabrication, solar panel fabrication, etc.

In one implementation, the invention is a flow restrictor forrestricting the flow of a gas. The flow restrictor has a first end, asecond end, and a longitudinal axis extending from the first end to thesecond end. A plurality of first layers extend from the first end to thesecond end along the longitudinal axis. A plurality of second layersextend from the first end to the second end along the longitudinal axis.A first aperture at the first end is defined by a first layer of theplurality of first layers and the plurality of second layers. A secondaperture at the second end is defined by the first layer of theplurality of first layers and the plurality of second layers. A flowpassage is defined by the first layer of the plurality of first layersand the plurality of second layers, the flow passage extending from thefirst aperture to the second aperture.

In another implementation, the invention is a mass flow controlapparatus for delivery of a fluid, the mass flow control apparatushaving a valve comprising an inlet passage, an outlet passage, a valveseat, and a closure member. The mass flow control apparatus also has aflow restrictor, the flow restrictor positioned in one of the inletpassage or the outlet passage. The flow restrictor has a first end, asecond end, and a longitudinal axis extending from the first end to thesecond end. A plurality of layers extend substantially parallel to thelongitudinal axis. A first aperture is located at the first end and asecond aperture is located at the second end. A flow passage is definedby the plurality of layers, the flow passage fluidly coupled to thefirst aperture and the second aperture.

In yet another implementation, the invention is a method ofmanufacturing a flow restrictor. First, a plurality of layer blanks areprovided, the layer blanks having a first edge, a second edge oppositethe first edge, a third edge, a fourth edge opposite the third edge, afront face, and a rear face opposite the front face. A first cavity isformed in the front face of a first one of the plurality of layerblanks. The plurality of layer blanks are stacked. Subsequently, theplurality of layer blanks are bonded to form a resistor stack having afirst unfinished end and an opposite second unfinished end. The firstunfinished end of the resistor stack is formed by the first edges of theplurality of layer blanks and the second unfinished end of the resistorstack is formed by the second edges of the plurality of layer blanks.Finally, material is removed from the first unfinished end of the layerstack to expose the first cavity and form a first aperture.

In one implementation, the invention is a seal for a gas flowrestrictor, the seal having a first end, a second end, and an aperturefor receiving the flow restrictor to form a fluid tight connectionbetween the flow restrictor and the seal.

In another implementation, the invention is a valve assembly, the valveassembly having a valve, a flow restrictor, and a seal. The valve has apassage. The flow restrictor has a first end, a second end, alongitudinal axis extending from the first end to the second end, and asealing portion located between the first end and the second end alongthe longitudinal axis. The seal is in contact with the sealing portionof the flow restrictor and the passage of the valve.

In yet a further implementation, the invention is a valve assembly, thevalve assembly having a valve, the valve having a first passage, asecond passage, a first sealing recess, and a second recess. The valveassembly has a base having a third sealing recess and a fourth sealingrecess. The valve assembly has a flow restrictor, the flow restrictorhaving a first end, a second end, a longitudinal axis extending from thefirst end to the second end, and a surface of the flow restrictorlocated between the first end and the second end along the longitudinalaxis. Finally, the valve assembly has a seal in contact with the surfaceof the flow restrictor and the first sealing recess of the valve.

In another implementation, the invention is a valve assembly, the valveassembly having a valve, a flow restrictor, and a seal. The valve has aport, a passage, and a basin, the passage extending between the port anda floor of the basin. The flow restrictor has a first end, a second end,a longitudinal axis extending from the first end to the second end, anda sealing portion located between the first end and the second end alongthe longitudinal axis. The seal is in contact with both the sealingportion of the flow restrictor and the floor of the basin.

In one implementation, the invention is a seal for a gas flowrestrictor, the seal having a first end, a second end, and an apertureconfigured to receive the flow restrictor, the aperture forming afluid-tight connection between the flow restrictor and the seal.

In another implementation, the invention is a valve assembly, the valveassembly having a valve, a flow restrictor, and a seal. The valve has apassage. The flow restrictor has a first end, a second end, alongitudinal axis extending from the first end to the second end, and asealing portion located between the first end and the second end alongthe longitudinal axis. The seal is in contact with the sealing portionof the flow restrictor and surrounding the passage of the valve.

Further areas of applicability of the present technology will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred implementation, are intended for purposes ofillustration only and are not intended to limit the scope of thetechnology.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention of the present disclosure will become more fullyunderstood from the detailed description and the accompanying drawings,wherein:

FIG. 1 is a schematic of a process utilizing one or more laminar flowrestrictors.

FIG. 2 is a schematic of a mass flow controller as may be utilized inthe process of FIG. 1 .

FIG. 3 is a perspective view of a first embodiment of a laminar flowrestrictor as may be utilized in the mass flow controller of FIG. 2 .

FIG. 4 is a perspective view illustrating a portion of the layersforming the flow restrictor of FIG. 3 .

FIG. 5A is an end view of the portion of the flow restrictor of FIG. 4 .

FIG. 5B is a detail view of the area VB of FIG. 5A.

FIG. 6 is an exploded perspective view of the portion of the flowrestrictor of FIG. 4 .

FIG. 7 is a cross-sectional view of the portion of the flow restrictorof FIG. 4 , taken along line VII-VII.

FIG. 8 is a top view of a first layer of the flow restrictor of FIG. 3 .

FIG. 9 is a top view of a second layer of the flow restrictor of FIG. 3.

FIG. 10 is a perspective view of a second embodiment of a laminar flowrestrictor.

FIG. 11 is a perspective view illustrating a portion of the layersforming the flow restrictor of FIG. 10 .

FIG. 12A is an end view of the portion of the flow restrictor of FIG. 11.

FIG. 12B is a detail view of the area XIIB of FIG. 12A.

FIG. 13 is an exploded perspective view of the portion of the flowrestrictor of FIG. 11 .

FIG. 14 is a cross-sectional view of the portion of the flow restrictorof FIG. 11 , taken along line XIV-XIV.

FIG. 15 is a top view a first layer of the flow restrictor of FIG. 10 .

FIG. 16 is a top view a second layer of the flow restrictor of FIG. 10 .

FIG. 17 is a perspective view of a portion of a third embodiment of alaminar flow restrictor.

FIG. 18 is an end view of the portion of the flow restrictor of FIG. 17.

FIG. 19 is an exploded perspective view of the portion of the flowrestrictor of FIG. 17 .

FIG. 20 is a cross-sectional view of the portion of the flow restrictorof FIG. 17 , taken along line XX-XX.

FIG. 21 is a top view of a first layer of the flow restrictor of FIG. 17.

FIG. 22 is a top view of a second layer of the flow restrictor of FIG.17 .

FIG. 23 is a perspective view of a portion of a fourth embodiment of alaminar flow restrictor.

FIG. 24 is an end view of the portion of the flow restrictor of FIG. 23.

FIG. 25 is an exploded perspective view of the portion of the flowrestrictor of FIG. 23 .

FIG. 26 is a cross-sectional view of the portion of the flow restrictorof FIG. 23 , taken along line XXVI-XXVI.

FIG. 27 is a top view of a first layer of the flow restrictor of FIG. 23.

FIG. 28 is a top view of a second layer of the flow restrictor of FIG.23 .

FIG. 29 is a top view of a third layer of the flow restrictor of FIG. 23.

FIG. 30 is a perspective view of a fifth embodiment of a laminar flowrestrictor.

FIG. 31 is a perspective view illustrating a portion of the layersforming the flow restrictor of FIG. 30 .

FIG. 32 is an end view of the portion of the flow restrictor of FIG. 31.

FIG. 33 is an exploded perspective view of the portion of the flowrestrictor of FIG. 31 .

FIG. 34 is a cross-sectional view of the portion of the flow restrictorof FIG. 31 , taken along line XXXIV-XXXIV.

FIG. 35 is a top view a first layer of the flow restrictor of FIG. 31 .

FIG. 36 is a top view a second layer of the flow restrictor of FIG. 31 .

FIG. 37 is an exploded perspective view of a plurality of layer blanksillustrating methods of manufacturing the disclosed flow restrictors.

FIG. 38 is a top view of a first layer of the invention of FIG. 37 .

FIG. 39 is a top view of a second layer of the invention of FIG. 37 .

FIG. 40 is a perspective view of a resistor stack prior to finishingaccording to the invention of FIG. 37 .

FIG. 41 is a perspective view of a resistor stack after finishingaccording to the invention of FIG. 37 .

FIG. 42 is a schematic of a process utilizing one or more flowrestrictors.

FIG. 43 is a schematic of a mass flow controller as may be utilized inthe process of FIG. 42 .

FIG. 44 is a schematic view of a valve incorporating a first embodimentof a flow restrictor and seal as may be utilized in the mass flowcontroller of FIG. 43 .

FIG. 45 is a perspective view of the first embodiment of the flowrestrictor and seal as may be utilized in the valve of FIG. 44 .

FIG. 46 is a cross-sectional view of the flow restrictor and seal ofFIG. 45 , taken along line XLVI-XLVI.

FIG. 47 is a perspective view of the flow restrictor of FIG. 45 withoutthe seal.

FIG. 48 is a perspective view of the seal of FIG. 45 without the flowrestrictor.

FIG. 49 is a schematic view of a valve incorporating a second embodimentof a flow restrictor and seal as may be utilized in the mass flowcontroller of FIG. 43 .

FIG. 50 is a perspective view of the second embodiment of the flowrestrictor and seal as may be utilized in the valve of FIG. 49 .

FIG. 51 is a cross-sectional view of the flow restrictor and seal ofFIG. 50 , taken along line LI-LI.

FIG. 52 is a perspective view of the seal of FIG. 50 without the flowrestrictor.

FIG. 53 is a cross-sectional view of the seal of FIG. 52 , taken alongline LIII-LIII.

FIG. 54 is a front view of the seal of FIG. 52 .

FIG. 55 is a top view of the seal of FIG. 55 .

FIG. 56 is a perspective view of another embodiment of a laminar flowrestrictor.

FIG. 57 is a perspective view illustrating a portion of the layersforming the flow restrictor of FIG. 56 .

FIG. 58 is an end view of the portion of the flow restrictor of FIG. 57.

FIG. 59 is an exploded perspective view of the portion of the flowrestrictor of FIG. 57 .

FIG. 60 is a cross-sectional view of the portion of the flow restrictorof FIG. 57 , taken along line LX-LX.

FIG. 61 is a top view a first layer of the flow restrictor of FIG. 57 .

FIG. 62 is a top view a second layer of the flow restrictor of FIG. 67 .

FIG. 63 is a perspective view of an apparatus for controlling flow.

FIG. 64 is a cross-sectional view of the apparatus for controlling flowof FIG. 63 , taken along line LXIV-LXIV.

FIG. 65 is an enlarged view of a portion of the cross-sectional view ofFIG. 64 .

DETAILED DESCRIPTION

The description of illustrative embodiments according to principles ofthe present invention is intended to be read in connection with theaccompanying drawings, which are to be considered part of the entirewritten description. In the description of embodiments of the inventiondisclosed herein, any reference to direction or orientation is merelyintended for convenience of description and is not intended in any wayto limit the scope of the present invention. Relative terms such as“lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,”“down,” “left,” “right,” “top” and “bottom” as well as derivativesthereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should beconstrued to refer to the orientation as then described or as shown inthe drawing under discussion. These relative terms are for convenienceof description only and do not require that the apparatus be constructedor operated in a particular orientation unless explicitly indicated assuch. Terms such as “attached,” “affixed,” “connected,” “coupled,”“interconnected,” and similar refer to a relationship wherein structuresare secured or attached to one another either directly or indirectlythrough intervening structures, as well as both movable or rigidattachments or relationships, unless expressly described otherwise.Moreover, the features and benefits of the invention are illustrated byreference to the preferred embodiments. Accordingly, the inventionexpressly should not be limited to such preferred embodimentsillustrating some possible non-limiting combinations of features thatmay exist alone or in other combinations of features; the scope of theinvention being defined by the claims appended hereto.

SECTION I

The present invention is directed to a laminar flow restrictor for usein an apparatus for controlling gas flow. In some embodiments, theapparatus may function as a mass flow controller to deliver a known massflow of gas to a semiconductor or similar process. Semiconductorfabrication is one industry which demands high performance in control ofgas flows. As semiconductor fabrication techniques have advanced,customers have recognized the need for flow control devices withincreased accuracy and repeatability in the mass of the delivered gasflows. Modern semiconductor processes require that the mass of the gasflow is tightly controlled, the response time minimized, and the gasflow is highly accurate. The present invention delivers improvedaccuracy and repeatability in the delivered flows.

FIG. 1 shows a schematic of an exemplary processing system 1000utilizing one or more laminar flow restrictors. The processing system1000 may utilize a plurality of apparatus for controlling flow 100fluidly coupled to a processing chamber 1300. The plurality of apparatusfor controlling flow 100 are used to supply one or more differentprocess gases to the processing chamber 1300. Articles such assemiconductors may be processed within the processing chamber 1300.Valves 1100 isolate each of the apparatus for controlling flow 100 fromthe processing chamber 1300, enabling each of the apparatus forcontrolling flow 100 to be selectively connected or isolated from theprocessing chamber 1300, facilitating a wide variety of differentprocessing steps. The processing chamber 1300 may contain an applicatorto apply process gases delivered by the plurality of apparatus forcontrolling flow 100, enabling selective or diffuse distribution of thegas supplied by the plurality of apparatus for controlling flow 100. Inaddition, the processing system 1000 may further comprise a vacuumsource 1200 which is isolated from the processing chamber 1300 by avalve 1100 to enable evacuation of process gases or facilitate purgingone or more of the apparatus for controlling flow 100 to enableswitching between process gases in the same apparatus for controllingflow 100. Optionally, the apparatus for controlling flow 100 may be massflow controllers, flow splitters, or any other device which controls theflow of a process gas in a processing system. Furthermore, the valves1100 may be integrated into the apparatus for controlling flow 100 if sodesired.

Processes that may be performed in the processing system 100 may includewet cleaning, photolithography, ion implantation, dry etching, atomiclayer etching, wet etching, plasma ashing, rapid thermal annealing,furnace annealing, thermal oxidation, chemical vapor deposition, atomiclayer deposition, physical vapor deposition, molecular beam epitaxy,laser lift-off, electrochemical deposition, chemical-mechanicalpolishing, wafer testing, or any other process utilizing controlledvolumes of a process gas.

FIG. 2 shows a schematic of an exemplary mass flow controller 101, whichis one type of apparatus for controlling flow 100 that may be utilizedin the processing system 1000. The mass flow controller 101 has a gassupply of a process gas fluidly coupled to an inlet 104. The inlet isfluidly coupled to a proportional valve 120 which is capable of varyingthe volume of process gas flowing through the proportional valve 120.The proportional valve 120 meters the mass flow of process gas whichpasses to the P1 volume 106. The proportional valve 120 is capable ofproviding proportional control of the process gas such that it need notbe fully open or closed, but instead may have intermediate states topermit control of the mass flow rate of process gas.

A P1 volume 106 is fluidly coupled to the proportional valve 120, the P1volume 106 being the sum of all the volume within the mass flowcontroller 101 between the proportional valve 120 and a flow restrictor160. A pressure transducer 130 is fluidly coupled to the P1 volume 106to enable measurement of the pressure within the P1 volume 106. Anon/off valve 150 is located between the flow restrictor 160 and theproportional valve 120 and may be used to completely halt flow of theprocess gas out of the P1 volume 106. Optionally, the flow restrictor160 may be located between the on/off valve 150 and the proportionalvalve 120 in an alternate configuration. Finally, the flow restrictor160 is fluidly coupled to an outlet 110 of the mass flow controller 101.In the processing system, the outlet 110 is fluidly coupled to a valve1100 or directly to the processing chamber 1300.

Internal to the first on/off valve 150 is a valve seat and a closuremember. When the apparatus 100 is delivering process gas, the firston/off valve 150 is in an open state, such that the valve seat and theclosure member are not in contact. This permits flow of the process gas,and provides a negligible restriction to fluid flow. When the firston/off valve 150 is in a closed state the closure member and the valveseat are biased into contact by a spring, stopping the flow of processgas through the first on/off valve 150.

The flow restrictor 160 is used, in combination with the proportionalvalve 120, to meter flow of the process gas. In most embodiments, theflow restrictor 160 provides a known restriction to fluid flow. Thefirst characterized flow restrictor 160 may be selected to have aspecific flow impedance so as to deliver a desired range of mass flowrates of a given process gas. The flow restrictor 160 has a greaterresistance to flow than the passages upstream and downstream of the flowrestrictor 160.

Optionally, the mass flow controller 101 comprises one or more P2pressure transducers downstream of the flow restrictor 160 and theon/off valve 150. The P2 pressure transducer is used to measure thepressure differential across the flow restrictor 160. In someembodiments, the P2 pressure downstream of the flow restrictor 160 maybe obtained from another apparatus 100 connected to the processingchamber, with the readings communicated to the mass flow controller 101.

Optionally, temperature sensors may be employed to further enhance theaccuracy of the mass flow controller 101. They may be mounted in thebase of the mass flow controller 101 near the P1 volume 106. Additionaltemperature sensors may be employed in a variety of locations, includingthe proportional valve 120, the pressure transducer 130, and the on/offvalve 150.

Turning to FIGS. 3-9 , a first embodiment of the flow restrictor 160 isshown in greater detail. The flow restrictor 160 is constructed as aplurality of layers forming a restrictor stack 170. The restrictor stack170 may take the form of an elongated rectangular shape as shown in FIG.3 . The flow restrictor 160 extends from a first end 161 to a second end162 along a longitudinal axis A-A. A plurality of layers 210 comprisingflow passages are sandwiched between a plurality of outer layers 220which do not comprise flow passages. The flow restrictor 160 has a firstside 163 formed of the pluralities of layers 210, 220 and an oppositesecond side 164. The flow restrictor 160 further comprises a front face165 and an opposite rear face 166. The outer layers 220 enclose the flowpassages on opposite sides of the layers 210 comprising flow passages.The outer layers 220 may or may not have the same thickness as thelayers 210 comprising flow passages. A selection of the layers 210 isshown in FIG. 4 , which illustrates portions of the flow passages andthe configuration of the layers 210. Each of the layers 210 extend froma first end 213 to a second end 214. Portions of the plurality of flowpassages can be seen in FIG. 4 . The details of the flow passages willbe discussed in greater detail below.

Turning to FIGS. 5A and 5B, the layers 210 comprise a plurality ofapertures 212 formed at opposite ends 213, 214 of the layers 210. Thisenables gas to flow along the layers 210 from the first end 213 to thesecond end 214 along the longitudinal axis A-A. In alternateembodiments, the apertures 212 need not be on opposite ends and mayinstead be formed on adjacent sides or may be formed exclusively on asingle end. The apertures 212 may also be formed so that gas flowsacross the shorter direction of the rectangular layers 210,perpendicular to the longitudinal axis A-A. The layers 210 also need notbe rectangular and may be square or any other desired shape. It isfurther contemplated that an aperture may be formed into the plane ofthe layers 210, permitting gas to flow perpendicular to the planes ofthe layers 210, then turn a corner and flow in the plane of the layers210. The specific arrangement of the apertures 212, the shape of thelayers 210, and the shape of the resulting flow restrictor 160 may beadapted as desired depending on the shape of the flow passage whichreceives the resulting flow restrictor 160. It is even contemplated thatthe flow restrictor 160 may have an annular configuration, withapertures 212 formed into a circumference of the flow restrictor 160and/or apertures 212 formed so that gas flows perpendicular to theplanes of some or all of the layers 210.

FIG. 6 shows an exploded view of the layers 210. The layers 210 comprisetwo first layers 230 and two second layers 260. As best seen in FIGS. 8and 9 , the first layer 230 has a first side 231, a second side 232, athird side 233, a fourth side 234, a front face 235, and an oppositerear face 236. The second layer 260 has a first side 261, a second side262, a third side 263, a fourth side 264, a front face 265, and anopposite rear face 266. The first layer 230 has a series of flowpassages comprising entry passages 237, U passages 238, and longitudinalpassages 239. The entry passages and the U passages are each only formedinto a portion of the thickness of the first layer 230 while thelongitudinal passages 239 extend through the entirety of the thicknessof the first layer 230. The second layer 260 also has entry passages 267and U passages 268 formed into the front face 265 that correspond to theentry passages 237 and U passages 238 of the first layer 240. When afirst layer 230 and a second layer 260 are stacked with the front faces235, 265 facing one another, the entry passages 237, 267 form apertures212 on the first and second sides 231, 261, 232, 262 of the layers 230,260. As is best shown in FIG. 7 , in combination with additional firstlayers 230 and second layers 260, a plurality of flow passages 270 areformed, extending from apertures 212 on one end 213 of the plurality oflayers 210 to the opposite second end 214 of the plurality of layers210.

Returning to FIG. 5A, the apertures 212 have a first edge 215, a secondedge 216, a third edge 217, and a fourth edge 218. The first edge 215 isformed by the first layer 230, the second edge 216 is formed by thesecond layer 260, and the third and fourth edges 217, 218 are eachformed by a portion of the first layer 230 and a portion of the secondlayer 260.

The flow passages 270 may be varied in any desired manner to achieve adesired flow impedance. For instance, the number of flow passages 270may be increased or decreased by reducing or increasing the number ofthe plurality of layers 210. Furthermore, the length of the flowpassages 270 may be increased or decreased by changing the number oftimes that the flow passages 270 double back on themselves, changing theresulting number of U passages 238, 268 and longitudinal passages 239. Agreater or fewer number of flow passages 270 may be formed into pairs offirst and second layers 230, 260. The width of the flow passages 270 mayalso be increased or decreased, and the thickness of the first andsecond layers 230, 260 may be varied. Indeed, it is not necessary thatthe same thickness be used for every pair of first and second layers230, 260. Each layer within the plurality of layers 210 could beindividually varied to alter the resulting flow impedance of the flowrestrictor 160.

The flow restrictor 160 is manufactured by first etching each of thelayers 210 individually or in an array. The layers 210 may all be formedof the same material or may be formed of different materials. Theetching may be carried out in a single step or in a series of steps toachieve the multiple depths required. Alternative processes such aslaser ablation, micromachining, or other known processes may also beused. Once the plurality of layers 210 have been formed, they areassembled with the non-etched outer layers 220 and joined by diffusionbonding. Again, alternative techniques such as conventional bonding withadhesives, welding, or similar processes may also be used as is known inthe art. The resulting stack of layers 210, 220 is joined, sealing theflow passages 270 and forming the flow restrictor 160. Subsequentfinishing steps can be performed to alter the overall shape or size ofthe flow restrictor 160 to suit the dimensions of the flow passages intowhich the flow restrictor 160 is installed. These processes may includegrinding, machining, laser cutting, water jetting, or other knowntechniques. Indeed, the flow restrictor 160 does not need to remainrectangular and may be formed into cylindrical shapes as will bediscussed further below.

Turning to FIGS. 10-16 , a second embodiment of the flow restrictor 300is best shown in FIG. 10 . Where not explicitly noted, the referencenumerals are identical to those of the first embodiment of the flowrestrictor 160. The second embodiment of the flow restrictor 300 extendsfrom a first end 302 to a second end 303 along a longitudinal axis A-Aand is also formed of a plurality of layers 310 having flow passages anda plurality of outer layers 320 which do not have flow passages. Afterbonding, the layers 310, 320 are post-processed into a cylindrical shapewhich facilitates insertion into a cylindrical bore, enabling easyinstallation of the flow restrictor 300 into a valve or other flowdevice.

As shown in FIG. 11 , a selection of the layers 310 are shown inperspective. The layers 310 extend from a first end 313 to a second end314 opposite the first end 313. FIGS. 12A and 12B best illustrate theapertures 312 formed into the first end 313 of the layers 310. As canalso be seen, the layers 310 comprise two first layers 330 and twosecond layers 360. As best seen in FIG. 12B, the apertures 312 have afirst edge 315, a second edge 316 opposite the first edge 315, a thirdedge 317, and a fourth edge 318 opposite the third edge 317. The firstand second edges 315, 316 are formed by the first layers 330. The thirdand fourth edges 317, 318 are each formed by the second layer 360.

An exploded view of the layers 310 is shown in FIG. 13 , betterillustrating the flow passages of the restrictor 300. FIGS. 15 and 16illustrate the first layer 330 and the second layer 360, respectively.The first layer 330 has a first side 331, a second side 332, a thirdside 333, a fourth side 334, a front face 335, and an opposite rear face336. The second layer 360 has a first side 361, a second side 362, athird side 363, a fourth side 364, a front face 365, and an oppositerear face 366. The first layer 330 has a series of longitudinal passages339 that terminate in layer transition apertures 340. The longitudinalpassages 339 and the layer transition apertures 340 extend through theentirety of the first layer 330. The second layer 360 has notches 369that extend from the first and second sides 361, 362. The notches 369also extend through the entirety of the second layer 360. As can be bestseen in FIG. 14 , the apertures 312 are formed by the open ends of thenotches 369 when the layers 330, 360 are alternately stacked as shown.Flow passages 370 are formed by the stacking of the layers 330, 360 asshown. In alternate embodiments, the layer transition apertures may beformed in a variety of shapes and may be formed with or without flowpassage contouring at the ends of the channel, or with contouring ofdifferent shapes.

Once again, a plurality of the layers 330, 360 are stacked and assembledwith the outer layers 320. The layers are then bonded through diffusionbonding or a similar technique. The resulting resistor stack is thenground or machined into a cylindrical shape as shown in FIG. 10 . Thiscylindrical shape also incorporates annular grooves which facilitate themounting of a seal which seals the flow restrictor 300 into a bore of adevice to ensure that the only gas passing by the flow restrictor 300must pass through the passages 370. In other embodiments, the final partmay be machined into different shapes, or alternatively left in its rawshape formed by the bonded resistor stack.

A third embodiment of the flow restrictor 400 is shown in FIGS. 17-22 .FIG. 17 shows a selection of the plurality of layers 410 forming theflow passages of the flow restrictor 400. The outer layers are not shownin this embodiment as they are substantially identical to those of theother embodiments. The plurality of layers 410 extend from a first end413 to a second end 414 opposite the first end 413. As best shown inFIG. 18 , apertures 412 are formed in the first end 413 and the secondend 414 to permit passage of gas into and out of the flow restrictor400. FIG. 19 shows an exploded view of the plurality of layers 410 tobetter illustrate the flow passages. As can be seen, the plurality oflayers 410 comprise two first layers 430 and two second layers 460.

FIGS. 21 and 22 illustrate the first layer 430 and the second layer 460,respectively. The first layer 430 has a first side 431, a second side432, a third side 433, a fourth side 434, a front face 435, and anopposite rear face 436. The second layer 460 has a first side 461, asecond side 462, a third side 463, a fourth side 464, a front face 465,and an opposite rear face 466. The first layer 430 has a series oflongitudinal passages 439 having an elongated configuration withstraight sides and a radius at each end. The second layer 460 hasnotches 469 that transition from a u-shape having parallel sides toangled sides which increase in width as they approach the first side 461or second side 462 of the second layer 460. The notches 469 overlap withthe longitudinal passages 439 when the first and second layers arealigned. The second layer 460 also has D-shaped apertures 468 whichallow the connection of two adjacent longitudinal passages 439 toincrease the effective length of the flow passage from one aperture 412to another aperture 412. There is no limit to the number of D-shapedapertures 468 which may be employed. Furthermore, there is no need tolimit the apertures 468 to a D shape, and they may be any desired shapeto facilitate a connection between adjacent longitudinal passages 439.In alternate embodiments the notches 469 can be shaped differently. Forinstance, shapes such as rectangular, wedge, or other shapes may beused. Additionally, longitudinal passages 439 can have contouring inthem to improve flow characteristics. Thus, the longitudinal passages439 need not be formed with a constant width, and may have varyingwidths at either ends or anywhere along their length. In yet furtherembodiments a third layer (or a plurality of layers) can be interleavedbetween the first layer 430 and the second layer 460 such that eachfirst layer 430 only contacts one second layer 460, and the apertures468 between subsequent sheets do not allow flow transitions except foradjacent first and second layers 430, 460.

As can be best seen in FIG. 20 , the apertures 412 are formed by theopen ends of the notches 469 when the layers 430, 460 are alternatelystacked as shown. Flow passages 470 are formed by the stacking of thelayers 430, 460 as shown. The layers 430, 460 are of equal thickness inthis embodiment, but may have different thicknesses if desired.

A fourth embodiment of the flow restrictor 500 is shown in FIGS. 23-29 .FIG. 23 shows a selection of the plurality of layers 510 forming theflow passages of the flow restrictor 500. The outer layers are not shownin this embodiment as they are substantially identical to those of theother embodiments. The plurality of layers 510 extend from a first end513 to a second end 514 opposite the first end 513. As best shown inFIG. 24 , apertures 512 are formed in the first end 513 and the secondend 514 to permit passage of gas into and out of the flow restrictor500. FIG. 25 shows an exploded view of the plurality of layers 510 tobetter illustrate the flow passages. As can be seen, the plurality oflayers 510 comprise a first layer 530, a second layer 560, and a thirdlayer 580.

FIGS. 27-29 illustrate the first layer 530, the second layer 560, andthe third layer 580, respectively. The first layer 530 has a first side531, a second side 532, a third side 533, a fourth side 534, a frontface 535, and an opposite rear face 536. The second layer 560 has afirst side 561, a second side 562, a third side 563, a fourth side 564,a front face 565, and an opposite rear face 566. The first layer 530 hasa series of longitudinal passages 539 having an elongate configurationwith straight sides and a radius at each end. The second layer 560 hasnotches 569 that transition from a u-shape having parallel sides toangled sides which increase in width as they approach the first side 561or second side 562 of the second layer 560. The notches 569 overlap withthe longitudinal passages 539 when the first and second layers arealigned. The third layer 580 has a first side 581, a second side 582, athird side 583, a fourth side 584, a front face 585, and an oppositerear face 586. As can be best seen in FIG. 26 , the apertures 512 areformed by the open ends of the notches 569 when the layers 530, 560 arealternately stacked as shown. Flow passages 570 are formed by thestacking of the layers 530, 560 as shown. The layers 530, 560 are ofequal thickness in this embodiment, but may have different thicknessesif desired. The third layer may be useful for decreasing the density ofthe flow passages, ensuring that flow is more evenly distributed acrossthe cross-sectional area of the flow restrictor 500. This isparticularly useful for producing very high flow impedance flowrestrictors.

A fifth embodiment of the flow restrictor 600 is shown in FIGS. 30-36 .FIG. 30 shows the flow restrictor 600 in perspective. The flowrestrictor 600 extends from a first end 602 to a second end 603 and hasouter layers 620 which surround layers 610 which have flow passagestherein. A selection of the layers 610 are shown in FIG. 31 inperspective view. These layers 610 extend from a first end 613 to asecond end 614, with apertures 612 on the first and second ends 613,614. An exploded view of the layers 610 is shown in FIG. 33 ,illustrating two first layers 630 and two second layers 660.

The first layer 630 and the second layer 660 are illustrated in FIGS. 35and 36 . The first layer 630 has a first side 631, a second side 632, athird side 633, a fourth side 634, a front face 635, and an oppositerear face 636. The second layer 660 has a first side 661, a second side662, a third side 663, a fourth side 664, a front face 665, and anopposite rear face 666. The first layer 630 has a series of longitudinalpassages 639 having an elongated configuration which meet with U shapedportions 640 or with openings 641. The second layer 660 is free of anyflow passages or other features. As can be seen, in the flow restrictor600, gas remains exclusively on a single layer 630 and does nottransition between first and second layers 630, 660. Instead, it entersthrough an opening 641 at the first side 631, travels down alongitudinal passage 639, returns along a U shaped portion 640 at leasttwo times, then exits through an opening 641 on the second side 632. Theexact flow path may be altered to zig-zag, utilize more than two Ushaped portions 640, no U shaped portions 640, or take any other path onthe layer 630. However, it never flows through the second layer 660 inthis embodiment. The longitudinal passages 639, U shaped portions 640,and openings 641 all extend through the entirety of the thickness of thefirst layer 630. In alternate configurations, single sheet flow may beobtained by forming the flow passage depth only partially through thesheet such that the sheet dimensions remain intact during assembly priorto bonding.

As best shown in FIG. 34 , flow passages 670 are formed by the stackingof the layers 630, 660 as shown. The layers 630, 660 are of equalthickness in this embodiment, but may have different thicknesses ifdesired. The layers 630, 660 are formed individually of differentmaterials having a different reactivity when subjected to etchingchemicals. The material of the first layer 630 may be more reactive thanthe material of the second layer 660, facilitating effective etching ofthe first layer 630 without significant etching of the second layer 660.Layer pairs are formed by assembling one first layer 630 with one secondlayer 660. The layer pairs are then diffusion bonded so they cannot bereadily separated. As discussed above, other bonding techniques may beutilized. Then, the layer pairs are etched so that the flow passages 670are formed into the first layer 630 without etching the second layer660. The layer pairs are then assembled into the plurality of layers 610having flow passages 670. Outer layers 620 are also assembled with theplurality of layers 610 having the flow passages 670. Finally, thelayers 610, 620 are diffusion bonded together. Optionally, postprocessing such as grinding may be used to form the flow restrictor 600and adapt it for installation into a flow passage of a device.

It should be noted that the flow passages do not need to extend straightfrom one end of the flow restrictor to the other end of the flowrestrictor, or double back in parallel rows. Instead, it is conceivedthat the flow passages may zig-zag, arc, or take any other path neededto achieve the desired flow impedance in the completed flow restrictor.Multiple layer transitions may also be made, enabling the use of flowpassages which fork and rejoin, transition across more than two or threelayers, or the like. It is further conceived that flow restrictors mayincorporate features of specific embodiments in combination, such that ahybrid of the disclosed embodiments may be constructed. Theabove-disclosed restrictor designs can be used to achieve highly laminarflow and high part to part reproducibility. This high reproducibilityreduces calibration requirements when manufacturing flow control devicesutilizing one or more laminar flow elements.

Details illustrating a method of forming the flow restrictors accordingto the present invention are shown in FIGS. 37-41 . FIG. 37 shows aplurality of layer blanks 710 in an exploded view. Each of the layerblanks has a first edge 711, a second edge 712 opposite the first edge,a third edge 713, and a fourth edge 714 opposite the third edge. Thelayer blanks 710 further comprise a front face 715 and a rear face 716opposite the front face 715. The layer blanks 710 are formed into firstlayers 730 and second layers 760 as further illustrated in FIGS. 38 and39 . The first layer 730 is modified from a layer blank 710 by forming asecond cavity 732 into the first layer 730. The second layer 760 ismodified from a layer blank 710 by forming a first cavity 761 and athird cavity 763 into the second layer 760. The first, second, and thirdcavities 761, 732, 763 are formed into the front faces 715 of theirrespective first and second layers 730, 760. Preferably the cavities761, 732, 763 are formed through the thickness of the layers 730, 760.In some embodiments, some or all of the cavities 761, 732, 763 may beformed only partially through the thickness of the layers 730, 760. Inthe illustrated method, the cavities 761, 732, 763 are formed from thefront face 715 to the rear face 716. The cavities 761, 732, 763 arespaced from the first, second, third, and fourth edges 711, 712, 713,714 of the layer blanks 710.

The cavities 761, 732, 763 are formed by etching the layer blanks 710.Alternate processes are available such as micromachining, laserablation, or other known techniques. As illustrated in FIG. 40 , aresistor stack 770 is formed from the plurality of layers 730, 760.Subsequent to formation of the cavities 761, 732, 763, the layers 730,760 are stacked in alternating layers, ensuring that the layers 730, 760are kept in alignment so that the second cavity 732 overlaps with thefirst and third cavities 761, 763. The layers 730, 760 are then bondedto form the resistor stack 770 as a unitary component. The layers 730,760 may be bonded by diffusion bonding, welding, gluing, or any otherknown technique. In yet other embodiments, the second cavity 732 may bethe only cavity and the first and third cavities 761, 763 may beomitted. Thus, it is conceived that the second cavity 732 may be theonly cavity required where the flow passages are formed into a singlelayer.

The resistor stack 770 comprises a first unfinished end 771 formed bythe first edges 711 of the first and second layers 730, 760. An oppositesecond unfinished end 772 is formed by the second edges 712 of the firstand second layers 730, 760 of the resistor stack 770. As can be seen, nocavities are exposed on the unfinished ends 771, 772. In alternateembodiments, only one of the layers 730, 760 need have cavities, withthe other layers 730, 760 being free of cavities. This allows formationof resistors such as those shown in FIGS. 30-36 . In yet otherembodiments, three or more different types of layers may be utilizedsuch as is shown in FIGS. 23-27 . The layers need not be alternatelystacked, but instead may simply be separated from each other. Thus,un-modified layer blanks 710 may be interleaved with the first andsecond layers if so desired. Any combination of layers can be made solong as at least one flow passage is formed in the finished flowresistor.

FIG. 41 illustrates the resistor stack 770 after finishing operationshave been completed. These finishing operations can take one of twoalternative forms. In the first process, the unfinished ends 771, 772are broken off of the resistor stack 770 to expose the first and thirdcavities 761, 763. The exposed first and third cavities 761, 763 formapertures 712 on first and second finished ends 773, 774. This resultsin flow passages extending from the apertures 712 on the first finishedend 773 to the apertures 712 on the second finished end. Optionally,additional material removal operations can be done to the resistor stack770 prior to removal of the unfinished ends 771, 772. This has thebenefit of minimizing the amount of debris which enters the flowpassages, ensuring that the resulting flow restriction closely matchesthe theoretical flow restriction provided by the flow restrictor.Furthermore, manufacturing repeatability is greatly improved by ensuringthat debris cannot enter the flow passages.

In an alternative second process, the unfinished ends 771, 772 of theresistor stack 770 are removed through conventional material removalprocesses such as machining, milling turning, sawing, grinding,electrical discharge machining, or etching. Once the unfinished ends771, 772 are removed to form the finished ends 773, 774, the resistorstack 770 is rinsed with deionized water. An electropolish process isused to dissolve any remaining metal particles and produce a surfacehaving very low roughness. Next, deionized water is pumped through theflow passages to flush the electropolishing solution. The resistor stack770 is then dried and subsequently a nitric acid solution is used toremove any remaining free iron, phosphates, and sulfates. This resultsin a surface which is extremely clean and free of contaminants.

SECTION II

The present invention is directed to a seal for a flow restrictor foruse in an apparatus for controlling gas flow. In some embodiments, theapparatus may function as a mass flow controller to deliver a known massflow of gas to a semiconductor or similar process. Semiconductorfabrication is one industry which demands high performance in control ofgas flows. As semiconductor fabrication techniques have advanced,customers have recognized the need for flow control devices withincreased accuracy and repeatability in the mass of the delivered gasflows. Modern semiconductor processes require that the mass of the gasflow is tightly controlled, the response time minimized, and the gasflow is highly accurate. The present seals ensure that the flowrestrictor is sealed into its flow passage more effectively and at areduced cost.

FIG. 42 shows a schematic of an exemplary processing system 1000Autilizing one or more flow restrictors. The processing system 1000A mayutilize a plurality of apparatus for controlling flow 100A fluidlycoupled to a processing chamber 1300A. The plurality of apparatus forcontrolling flow 100A are used to supply one or more different processgases to the processing chamber 1300A. Articles such as semiconductorsmay be processed within the processing chamber 1300A. Valves 1100Aisolate each of the apparatus for controlling flow 100A from theprocessing chamber 1300A, enabling each of the apparatus for controllingflow 100A to be selectively connected or isolated from the processingchamber 1300A, facilitating a wide variety of different processingsteps. The processing chamber 1300A may contain an applicator to applyprocess gases delivered by the plurality of apparatus for controllingflow 100A, enabling selective or diffuse distribution of the gassupplied by the plurality of apparatus for controlling flow 100A. Inaddition, the processing system 1000A may further comprise a vacuumsource 1200A which is isolated from the processing chamber 1300A by avalve 1100A to enable evacuation of process gases or facilitate purgingone or more of the apparatus for controlling flow 100A to enableswitching between process gases in the same apparatus for controllingflow 100A. Optionally, the apparatus for controlling flow 100A may bemass flow controllers, flow splitters, or any other device whichcontrols the flow of a process gas in a processing system. Furthermore,the valves 1100A may be integrated into the apparatus for controllingflow 100A if so desired.

Processes that may be performed in the processing system 100A mayinclude wet cleaning, photolithography, ion implantation, dry etching,atomic layer etching, wet etching, plasma ashing, rapid thermalannealing, furnace annealing, thermal oxidation, chemical vapordeposition, atomic layer deposition, physical vapor deposition,molecular beam epitaxy, laser lift-off, electrochemical deposition,chemical-mechanical polishing, wafer testing, or any other processutilizing controlled volumes of a process gas.

FIG. 43 shows a schematic of an exemplary mass flow controller 101A,which is one type of apparatus for controlling flow 100A that may beutilized in the processing system 1000A. The mass flow controller 101Ahas a gas supply of a process gas fluidly coupled to an inlet 104A. Theinlet 104A is fluidly coupled to a proportional valve 120A which iscapable of varying the volume of process gas flowing through theproportional valve 120A. The proportional valve 120A meters the massflow of process gas which passes to the P1 volume 106A. The proportionalvalve 120A is capable of providing proportional control of the processgas such that it need not be fully open or closed, but instead may haveintermediate states to permit control of the mass flow rate of processgas.

A P1 volume 106A is fluidly coupled to the proportional valve 120A, theP1 volume 106A being the sum of all the volume within the mass flowcontroller 101A between the proportional valve 120A and a flowrestrictor 160A. A pressure transducer 130A is fluidly coupled to the P1volume 106A to enable measurement of the pressure within the P1 volume106A. An on/off valve 150A is located between the flow restrictor 160Aand the proportional valve 120A and may be used to completely halt flowof the process gas out of the P1 volume 106A. Optionally, the flowrestrictor 160A may be located between the on/off valve 150A and theproportional valve 120A in an alternate configuration. Finally, the flowrestrictor 160A is fluidly coupled to an outlet 110A of the mass flowcontroller 101A. In the processing system, the outlet 110A is fluidlycoupled to a valve 1100A or directly to the processing chamber 1300A. Inthe present embodiment, the flow restrictor 160A is located between theon/off valve 150A and the outlet 110A. In an alternate embodiment, theon/off valve 150A is located between the flow restrictor 160A and theoutlet 110A. Thus, the arrangement of the on/off valve 150A and the flowrestrictor 160A may be reversed.

Internal to the first on/off valve 150A is a valve seat and a closuremember. When the apparatus 100A is delivering process gas, the firston/off valve 150A is in an open state, such that the valve seat and theclosure member are not in contact. This permits flow of the process gasand provides a negligible restriction to fluid flow. When the firston/off valve 150A is in a closed state the closure member and the valveseat are biased into contact by a spring, stopping the flow of processgas through the first on/off valve 150A.

The flow restrictor 160A is used, in combination with the proportionalvalve 120A, to meter flow of the process gas. In most embodiments, theflow restrictor 160A provides a known restriction to fluid flow. Thefirst characterized flow restrictor 160A may be selected to have aspecific flow impedance so as to deliver a desired range of mass flowrates of a given process gas. The flow restrictor 160A has a greaterresistance to flow than the passages upstream and downstream of the flowrestrictor 160A.

Optionally, the mass flow controller 101A comprises one or more P2pressure transducers downstream of the flow restrictor 160A and theon/off valve 150A. The P2 pressure transducer is used to measure thepressure differential across the flow restrictor 160A. In someembodiments, the P2 pressure downstream of the flow restrictor 160A maybe obtained from another apparatus 100A connected to the processingchamber, with the readings communicated to the mass flow controller101A.

Optionally, temperature sensors may be employed to further enhance theaccuracy of the mass flow controller 101A. They may be mounted in thebase of the mass flow controller 101A near the P1 volume 106A.Additional temperature sensors may be employed in a variety oflocations, including the proportional valve 120A, the pressuretransducer 130A, and the on/off valve 150A.

Turning to FIG. 44 , a schematic of an on/off valve 150A is shown with afirst embodiment of the flow restrictor 160A located within an outletpassage 157A of the on/off valve 150A. The on/off valve 150A has aninlet passage 158A which allows process gas to flow into the valve 150A.A spring 156A biases a closure member 154A into contact with a valveseat 152A, preventing process gas from flowing when the valve 150A is ina closed state. When in an open state, the closure member 154A is movedso that it is spaced from the valve seat 152A, allowing process gas topass the valve seat 152A into the outlet 157A. The outlet 157A is formedas a cylindrical bore, but may also be formed as an oval, polygon, orany other shape. The flow restrictor 160A is inserted into the outlet157A with a seal 170A preventing gas flow between the flow restrictor160A and the wall 159A of the outlet 157A.

Turning to FIGS. 45-48 , the flow restrictor 160A and the seal 170A areshown in greater detail. FIG. 45 shows a perspective view of the flowrestrictor 160A and the seal 170A. The flow restrictor 160A extends froma first end 161A to a second end 162A along a longitudinal axis A-A. Theseal 170A is fitted to the flow restrictor 160A. The seal 170Acircumferentially surrounds the flow restrictor 160A and has an outersurface 171A. The seal 170A extends between a first end 172A and asecond end 173A along a longitudinal axis B-B. The longitudinal axis B-Bof the seal 170A is collinear with the longitudinal axis A-A of the flowrestrictor 160A. However, in alternate embodiments, the longitudinalaxis B-B of the seal 170A may not be collinear with the longitudinalaxis A-A of the flow restrictor 170A. In some embodiments, thelongitudinal axis B-B of the seal is angled with respect to thelongitudinal axis A-A of the flow restrictor 160A. In yet otherembodiments, the longitudinal axis B-B of the seal may be spaced butparallel to the longitudinal axis A-A of the flow restrictor 160A. Inyet other embodiments, the axes may be both angled and spaced from oneanother.

As best seen in FIG. 46 , the flow restrictor 160A has a sealing portion163A and an unsealed portion 166A. The unsealed portion 166A has a firstdiameter D1A and the sealing portion 163A has a second diameter D2A, thefirst diameter D1A being greater than the second diameter D2A. The seal170A further comprises an inner surface 174A which is in surface contactwith the sealing portion 163A of the flow restrictor 160A. The outersurface 171A has a third diameter D3A which is greater than either ofthe first and second diameters D1A, D2A. This results in an interferencefit between the wall 159A and the outer surface 171A and ensures thatthe seal 170A seals against the wall 159A of the outlet 157A whilesimultaneously preventing contact between the flow restrictor 160A andthe wall 159A. The inner surface 174A defines an aperture through whichthe flow restrictor 160A is received and through which all gas flowsgenerally along the axis B-B from the first end 161A to the second end162A of the flow restrictor 160A. In yet other embodiments, the sealingportion 163A extends the entire length of the flow restrictor 160A. Inyet further embodiments, the first diameter D1A may be the same diameteras the second diameter D2A. Preferably, the third diameter D3A has aninterference fit with the wall 159A. The third diameter D3A may also bethe same diameter as the second diameter D2A. Furthermore, the gas neednot enter from the first end 161A and exit the second end 162A of theflow restrictor, but may also enter through the circumference of theflow restrictor 160A. Flow of gas within the flow restrictor 160A neednot flow strictly along the axis B-B, but need only pass through theflow restrictor 160A and past the seal 170A rather than around it.

The sealing portion 163A has a seal receiving surface 165A and aplurality of ridges 164A used to improve sealing and retain the seal inplace. The second diameter D2A is reduced as compared with the firstdiameter D1A so as to provide room for the seal 170A and enhanceretention of the seal 170A on the flow restrictor 160A. The ridges 164Ahave a triangular cross-section and encircle the flow restrictor 160A.When the seal 170A is installed onto the sealing portion 163A of theflow restrictor 160A, the ridges 164A deform the seal 170A to furtherenhance the retention of the seal 170A. This ensures that the seal 170Ais maintained on the flow restrictor 160A when the flow restrictor ispressed into the outlet 157A. The third diameter D3A is typically aninterference fit with the outlet 157A, so substantial force may berequired to press the seal 170A into the outlet 157A depending on theextent of the interference. In the exemplary embodiment, the sealingportion 163A has two ridges 164A. In alternate embodiments, the sealingportion 163A may have greater or fewer ridges 164A. The cross-sectionalprofile of the ridges 164A may be rectangular, trapezoidal, or any othershape. In yet further variations, a texture may be formed on the sealreceiving surface 165A. This texture may be formed by knurling,grinding, or any other known process. In alternate embodiments, a singlemodel of flow restrictor 160A may be installed into a plurality ofoutlets 157A having differing diameters by modifying the thickness ofthe seal such that the third diameter D3A is modified to have a suitableinterference with the wall 159A of each of the respective outlets 157A.This configuration beneficially allows the restrictor to be installeddirectly against the seat of the valve, greatly reducing the volumeenclosed between the valve seat and the flow restrictor 160A. Inaddition, multiple valve geometries, bore sizes, and fitting geometriescan be accommodated by positioning the flow restrictor 160A within theoutlet 157A.

In use, process gas flows through the flow restrictor 160A from thefirst end 161A to the second end 162A. The seal 170A provides a closefit with both the flow restrictor 160A and the wall 159A of the outlet157A so as to prevent process gas from flowing around the flowrestrictor 160A. Although some leakage of gas is possible, this leakingis reduced to at least 1×10{circumflex over ( )}−7 atm-cc/sec whenHelium is used as a process gas. This leak rate ensures that anegligible volume of process gas flows around the flow restrictor 160Arather than through the flow restrictor 160A.

The seal 170A is preferably formed of a non-metallic material such as aplastic material. One exemplary material could bePolytetrafluoroethylene (also known as “PTFE” or “Teflon”). Alternatematerials may include metals, ceramics, or composite materials. The seal170A is preferably shrunk or stretched onto the flow restrictor 160A soas to ensure a tight fit between the seal receiving surface 165A and theinner surface 174A. However, other methods are contemplated. In yetfurther embodiments, the seal may be welded, bonded, or pressed onto theflow restrictor 160A so as to achieve a secure gas tight connectionbetween the seal 170A and the flow restrictor 160A. In yet anotherembodiment, a plurality of identical flow restrictors 160A are mountedto differing seals 170A to allow installation into different sizeoutlets 157A.

Turning to FIGS. 49-55 , a second embodiment of a flow restrictor 260Ais shown with a seal 270A. As can be seen in the schematic of FIG. 49 ,a valve 150A is illustrated. The valve 150A is substantially identicalto the valve 150A of FIG. 44 . However, instead of having a flowrestrictor pressed into the outlet 157A, a seal 270A is mounted betweena sealing surface 153A of the valve 150A and a sealing surface 291A of abase 290A, the base 290A comprising flow passages 292A which connect theon/off valve 150A to the various components of the mass flow controller101A or other apparatus for controlling flow 100A. The seal 270A isinstalled between the sealing surface 153A and the sealing surface 291Aand has a first seal ring 271A and a second seal ring 272A as best shownin FIGS. 50 and 51 . The first seal ring 271A and second seal ring 272Aare mounted to a gasket sheet 273A and extend beyond the gasket sheet273A to engage sealing recesses 155A, 295A of the valve 150A and thebase 290A, respectively. A plurality of apertures 274A are providedthrough the gasket sheet 273A to allow the passage of fasteners used tojoin the valve 150A to the base 290A. Additional holes 275A may be usedto facilitate manufacturing of the seal 270A or for other purposes suchas to seal additional flow passages.

As can be seen in FIG. 51 , the first seal ring 271A of the seal 270Areceives the flow restrictor 260A. The flow restrictor 260A extends froma first end 261A to a second end 262A along a longitudinal axis A-A. Asbest seen in FIGS. 51 and 52 , the first seal ring 271A has a first side276A and a second side 277A opposite the first side 276A, a longitudinalaxis B-B extending through the first seal ring 271A perpendicular to thefirst and second sides 276A, 277A. The first and second sides 276A, 277Aengage the sealing recesses 155A, 295A and are compressed between themwhen the valve 150A is mounted to the base 290A. The first seal ring271A also has an inner surface 278A which is generally cylindrical and asealing web 279A which extends across the inner surface 278A. A flowaperture 280A is formed in the sealing web 279A to receive the flowrestrictor 260A. The flow aperture 280A has a generally rectangularshape in the present embodiment, but in other embodiments it may becircular, elliptical, or any other shape suitable to accommodate acorresponding flow restrictor. The flow restrictor 260A has a generallyrectangular profile along the longitudinal axis and is a close fitwithin the flow aperture 280A. Once the flow restrictor 260A isinstalled in the flow aperture 280A, it can be welded, bonded, or pressfit to achieve a gas tight seal between the outer surface of the flowrestrictor 260A and the sealing web 279A, ensuring that no process gasescapes past the flow restrictor 260A without passing through the flowrestrictor 260A. The first seal ring 271A also has an outer surface 285Awhich may be of any size or diameter so long as the first seal ring 271Acan nest within the sealing recesses 155A, 295A. In alternateconfigurations, the sealing recesses 155A, 295A may be omitted. In yetfurther configurations, the inner surface 278A and outer surface 285Aneed not be cylindrical, and may be rectangular, ellipsoid, polygonal,or any other shape.

The second seal ring 272A also has a first side 281A and a second side282A. However, the second seal ring 272A differs from the first sealring 271A in that it has no corresponding sealing web. Instead, theinner surface 283A defines a flow aperture that enables the passage ofprocess gas without significant flow impedance. Ideally, the flowpassages and the second seal ring 272A provide no restriction to fluidflow. In alternate embodiments, the seal 270A may comprise only thefirst seal ring 271A and be free of the second seal ring 272A or anyother components. Alternately, there may be more than one of the firstor second seal rings 271A, 272A.

In alternate embodiments, the flow aperture 280A of the first seal ring271A may be circular, rectangular, have a polygon shape, may comprisearcs, or may have any known shape. Thus, any cross-section of flowrestrictor may be accommodated in the seal ring 271A. In yet furtherembodiments, the seal ring 271A may be press fit, welded, bonded, orotherwise secured directly within a flow passage such as the outlet 157Aof the valve 150A or the flow passages 292A of the base 290A. In yetfurther embodiments, the gasket sheet 273A may be omitted, such that theseal is comprised only of the seal ring 271A. The seal 270A ispreferably constructed at least partially of a metal material. In themost preferred embodiments, the first and second seal rings 271A, 272Aare metallic.

During assembly, the seal 270A is placed between the valve 150A and thebase 290A and aligned so that the first and second seal rings 271A, 272Aalign with the sealing recesses 155A, 295A. The flow restrictor 260Athen extends into the outlet 157A and the corresponding flow passage292A in the base 290A. The flow restrictor 260A may be attached to thefirst seal ring 271A so that the seal is halfway along the length of theflow restrictor 260A, or it may be attached at any point along thelength of the flow restrictor 260A. It may even be attachedsubstantially flush with either the first or second end 261A, 262A.Furthermore, the seal 270A may be installed such that it is locatedwithin a portion of the valve 150A to minimize the distance between thevalve seat 152A and the flow restrictor 260A, minimizing the volumetherebetween. As noted previously, the seal 270A may also be configuredso that the flow restrictor 260A is positioned upstream of the valveseat 152A and positioned in the inlet 158A instead of the outlet 157A.The seal of this embodiment can reliably produce a seal with a Heliumleak rate better than 1×10{circumflex over ( )}−11 atm-cc/sec,substantially eliminating all flow of process gas around the flowrestrictor 260A.

SECTION III

Yet another embodiment of a flow restrictor 800 is shown in FIGS. 56-62. FIG. 56 shows the flow restrictor 800 in perspective. The flowrestrictor 800 extends from a first end 802 to a second end 803 and hasouter layers 820 which surround layers 810 which have flow passagestherein. A selection of the layers 810 are shown in FIG. 57 inperspective view. These layers 810 extend from a first end 813 to asecond end 814, with apertures 812 on the first and second ends 813,814. The apertures 812 are not exposed at the first and second ends 813,814 but will be exposed during subsequent processing steps described ingreater detail below. The apertures need not have a different width thanthe rest of the flow passage, and instead may merely be formed byexposing the flow passage in a subsequent material removal operation.

A plurality of alignment features 815 are formed around the periphery ofthe layers 810, 820 to facilitate alignment and bonding of the layers810, 820 to form the flow restrictor 800. The alignment features 815 mayalso be formed internal to the layers 810, 820 and may be formed asholes, slots, protuberances, or any other geometry that permitsalignment. The alignment features 815 may also be used to facilitatemass production, ensure that layers 810, 820 are not flipped orotherwise upside-down, or for any other purpose. An exploded view of thelayers 810 is shown in FIG. 59 , illustrating two first layers 830 andtwo second layers 860. Flow passages 870 are formed in the first layers830.

The first layer 830 and the second layer 860 are illustrated in FIGS. 61and 62 . The first layer 830 has a first side 831, a second side 832, athird side 833, a fourth side 834, a front face 835, and an oppositerear face 836. The second layer 860 has a first side 861, a second side862, a third side 863, a fourth side 864, a front face 865, and anopposite rear face 866. The first layer 830 has a series of longitudinalpassages 839 having an elongated configuration which extend from thefirst side 831 to the second side 832.

The second layer 860 is free of any flow passages or other features. Ascan be seen, in the flow restrictor 800, gas remains exclusively on asingle layer 830 and does not transition between first and second layers830, 860. The second layers form upper and lower boundaries of the flowpassages, but do not have flow passages formed therein. The longitudinalpassages 839 form the flow passages 870 when bounded by the secondlayers 860 on the front face 865 and the opposite rear face 866. Gasenters through an opening 841 at the first side 831, travels down alongitudinal passage 839, then exits through an opening 841 on thesecond side 832. The openings 841 are exposed in subsequent materialremoval operations as noted above to form the apertures 812. In someembodiments, the flow path may zig-zag, change direction, or take anyother path on the layer 830. However, it never flows through the secondlayer 860 in this embodiment. The longitudinal passages 839 and openings841 all extend through the entirety of the thickness of the first layer830. In alternate configurations, single sheet flow may be obtained byforming the flow passage depth only partially through the sheet suchthat the sheet dimensions remain intact during assembly prior tobonding.

As best shown in FIG. 58 , the flow passages 870 are formed by thestacking of the layers 830, 860 as shown. The layers 830, 860 are ofunequal thickness in this embodiment, but may have the same thickness ifdesired. Furthermore, thickness of the layers 830 or the number of flowpassages 870 can be altered to alter the restriction to fluid flow. Eachof the first layers 830 may be etched individually, then later bonded inan alternating sequence with the second layers 860 to form the pluralityof layers 810 having a plurality of flow passages 870 therein.Subsequently or concurrently, the outer layers 820 may be bondedtogether with the plurality of layers 810 to form the flow restrictor800. Finally, post-processing is performed which exposes the openings841 to form apertures 812 and allow fluid flow through the flow passages870. Post-processing may include machining, grinding, or othertechniques.

In other embodiments, the layers 830, 860 may be formed individually ofdifferent materials having a different reactivity when subjected toetching chemicals or may be formed of identical materials having thesame reactivity when subjected to etching chemicals. Layers may beformed in pairs are formed by assembling one first layer 830 with onesecond layer 860. The layer pairs are then diffusion bonded so theycannot be readily separated. As discussed above, other bondingtechniques may be utilized. Then, the layer pairs are etched so that theflow passages 870 are formed into the first layer 830 without etchingthe second layer 860. The layer pairs are then assembled into theplurality of layers 810 having flow passages 870. Outer layers 820 arealso assembled with the plurality of layers 810 having the flow passages870. Finally, the layers 810, 820 are diffusion bonded together.Optionally, post processing such as grinding may be used to form theflow restrictor 800 and adapt it for installation into a flow passage ofa device.

In one method of finishing the flow restrictor 800, the flow restrictor800 is formed by bonding the plurality of layers 810 and the outerlayers 820 as discussed above. Subsequent to bonding of the layers 810,820, the flow restrictor is machined to expose the outlets 841 and formthe apertures 812. During the machining process, the flow restrictor 800is machined to form a generally cylindrical shape suitable for insertioninto a passage of a valve.

Subsequently, the machined flow restrictor 800 is ultrasonicallycleaned. Nitrogen is then flowed through the flow passages 870 toeliminate particles. An electropolish process is then used to furtherclean the flow passages 870. Deionized water is used to rinse the flowpassages 870 and remove any electropolish solution within the flowpassages 870. A nitrogen purge is then flowed through the flow passages870 to remove the deionized water. Nitric acid is then flowed throughthe flow passages 870 to further remove particles and debris, followedby another deionized water purge and nitrogen purge. Finally, anotherdeionized water rinse is performed and the flow restrictor 800 is driedusing a heated gas flow. This results in clean flow passages 870 whichare free of debris or other particles such as machining remnants and thelike. The flow restrictors 800 are clean and deliver highly predictablerestrictions to fluid flow as a result of the processing operationsperformed thereon.

Turning to FIGS. 63 to 65 , an exemplary apparatus for controlling fluidflow 100 is illustrated. The apparatus 100 has a valve 900, the valve900 being either a proportional valve or an on/off valve. The valve 900has a passage 902 through which a fluid flows. The passage extends froma port 904 to a basin 906. The basin 906 has a floor 908 and a sidewall910. A seal 912 serves as a seat for the valve 900. A closure member 914engages the seal 912 to permit or prevent fluid flow through the valve900.

The seal 912 is illustrated in greater detail in FIG. 65 . The seal 912has an inner surface 920 which engages a sealing surface 880 of the flowrestrictor 800. The inner surface 920 forms an aperture which receivesthe flow restrictor 800 to form a fluid-tight connection between theflow restrictor and the seal. The inner surface 920 forms a first sealwhich seals against the sealing surface 880 of the flow restrictor.

The sealing surface 880 also engages an inner surface 916 of the passage902. The sealing surface 880 may form an interference fit with thepassage 902 and with the inner surface 920 of the seal 912. This enablesa fluid-tight connection between the flow restrictor 800 and both thepassage 902 and the seal 912. Alternately, the sealing surface 880 mayonly be sealed against one of the inner surface 920 of the seal 912 orthe inner surface 916 of the passage 902. The sealing surface 880 mayalso be referred to as a sealing portion because it interfaces with theinner surface 210 of the seal 912 to form the first seal.

The seal further comprises a seat surface 922, a floor surface 924, anda flange 926. The flange 926 engages a retainer component 927 whichmaintains the seal 912 in position within the basin 906. The floorsurface 924 rests against the floor 908 of the basin 906. The interfacebetween the floor surface 924 of the seal 912 and the floor 908 of thebasin 906 may also provide a second seal to prevent leakage of fluidpast the seal 912 and into the passage 902. The seat surface 922 engagesthe closure member 914 of the valve 900 to prevent fluid flow throughthe flow restrictor 800. Optionally, the seal 912 may be formed of anon-metallic material. The seal 912 may be formed of a polymer materialsuch as polytetrafluoroethylene. Alternately, it may be formed of ametallic or composite material.

As can be seen in FIGS. 64 and 65 , the flow restrictor 800 also has aclearance surface 882 which has a smaller diameter than the sealingsurface 880. This is done to provide clearance for the flow restrictor800 within the passage 902. The first end 813 of the flow restrictor 800is recessed with respect to the seat surface 922 to ensure that the flowrestrictor 800 does not interfere with the closure member 914 duringoperation of the valve 900. The second end 814 extends into the passage902 and does not extend to the port 904.

While the invention has been described with respect to specific examplesincluding presently preferred modes of carrying out the invention, thoseskilled in the art will appreciate that there are numerous variationsand permutations of the above described systems and techniques. It is tobe understood that other embodiments may be utilized, and structural andfunctional modifications may be made without departing from the scope ofthe present invention. Thus, the spirit and scope of the inventionshould be construed broadly as set forth in the appended claims.

1. A seal for a flow restrictor, the seal comprising: a first end; asecond end, a longitudinal axis extending from the first end to thesecond end; and an aperture configured to receive the flow restrictor,the aperture forming a fluid-tight connection between the flowrestrictor and the seal.
 2. The seal of claim 1 wherein the seal isconfigured to form a fluid-tight connection between the seal and a floorof a basin of a valve.
 3. The seal of claim 1 wherein the seal isnon-metallic.
 4. The seal of claim 1 wherein the seal is formed ofpolytetrafluoroethylene.
 5. The seal of claim 1 wherein the seal has afirst end and a second end, the seal extending from the first end to thesecond end along the longitudinal axis.
 6. The seal of claim 5 whereinthe second end is configured to form a fluid-tight connection betweenthe seal and a floor of a basin of a valve.
 7. The seal of claim 1wherein the seal comprises a flange projecting radially outward.
 8. Theseal of claim 7 wherein the flange is located at the second end of theseal.
 9. The seal of claim 7 wherein the flange forms a part of thesecond end of the seal.
 10. The seal of claim 1 wherein the first end ofthe seal comprises a seat surface configured to engage a closure memberof a valve.
 11. A valve assembly comprising: a valve comprising apassage; a flow restrictor, the flow restrictor comprising: a first end;a second end; a longitudinal axis extending from the first end to thesecond end; and a sealing portion located between the first end and thesecond end along the longitudinal axis; and a seal in contact with thesealing portion of the flow restrictor and surrounding the passage ofthe valve.
 12. The valve assembly of claim 11 wherein the seal is formedof polytetrafluoroethylene.
 13. The valve assembly of claim 11 whereinthe seal is non-metallic.
 14. The valve assembly of claim 11 wherein theseal extends from a first end to a second end along the longitudinalaxis.
 15. The valve assembly of claim 14 wherein the seal comprises afloor surface at the second end.
 16. The valve assembly of claim 14wherein the seal comprises a seat surface at the first end, the seatsurface configured to engage a closure member of the valve.
 17. Thevalve assembly of claim 11 wherein the flow restrictor further comprisesan unsealed portion, the unsealed portion extending into the passage ofthe valve.
 18. A valve assembly comprising: a valve comprising a port, apassage, and a basin, the passage extending between the port and a floorof the basin; a flow restrictor, the flow restrictor comprising: a firstend; a second end; a longitudinal axis extending from the first end tothe second end; and a sealing portion located between the first end andthe second end along the longitudinal axis; and a seal in contact withboth the sealing portion of the flow restrictor and the floor of thebasin.
 19. The valve assembly of claim 18 wherein the seal forms a firstseal and a second seal, the first seal between the sealing portion ofthe flow restrictor and an inner surface of the seal and the second sealbetween the floor of the basin and a floor surface of the seal.
 20. Thevalve assembly of claim 18 wherein the flow restrictor is in contactwith an inner surface of the seal and an inner surface of the passage ofthe valve.
 21. (canceled)